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IGCSE CHEMISTRY
CHAPTER 1
Question | Answer |
---|---|
Which change of state takes place during evaporation? | Liquid to gas |
In which process do particles move closer together but remain in motion? | Condensation |
A sugar cube is dropped into a hot tea cup of tea. The tea is not stirred. Name the statement explain why the tea becomes sweet? | The sugar cube dissolves and its molecules diffuse |
Name the statement that is an example of diffusion? | The smell of cooking spreads through a house |
A few drops of perfume were spilt on the floor. A few minutes later the perfume could be smell a few meters away. Which two processes had taken place? | Evaporation and diffusion |
Two gas jars each contain a different gas. The gas jars are connected and cover slips are removed. Which process has occured? | Diffusion |
A liquid is heated until it boils. Which result shows that the liquid in the test-tube is pure water? | The thermometer reeds 100 degrees Celsius |
An attempt was made to compress a gas and a solid using a piston. Which substance would be compressed and what is the reason for this? | A gas and the gas particles are far apart |
A gas jar of bromine vapour and a gas jar of air are set up. The glass slide is removed. Name the statement explains why the bromine and air mix together after one hour? | Molecules in bromine and air moved randomly |
Particles moving very slowly from an area of high concentration to an area of low concentration. Which process is being described above? | A substance diffusing through a liquid |
In which substance are the particles close together and slowly moving past each other? | Steam |
Aqueous lead nitrate and aqueous potassium iodide are added to a dish containing water. A yellow precipitate forms after a few minutes. Which process occurs before the precipitate forms? | Diffusion |
The molecules of the exhaust gasses of a car diffuse into the air. Name the statement describes what happens to these molecules next? | The molecules spread further into the air |
Compare the movement and arrangement of the molecules in solid nitrogen to those in nitrogen gas? Name 3 points. | Solid pattern is regular and gas pattern is random Solid distance is close and gas distance is far apart Solid movement vibrate and gas movement moving around |
A sealed container contains nitrogen gas. The pressure of the gas is due to the molecules of the gas hitting the walls of the container. Use the kinetic theory to explain why the pressure inside the container increases when the temperature in increased? | Particles have more energy and move faster and collide more frequently. |
Explain why nitrogen gas diffuses faster than chlorine gas? | Nitrogen has smaller molecules Nitrogen moves faster than chlorine molecules |
Explain why the nitrogen gas diffuses faster at the higher temperature. | At higher temperature molecules move faster |
Some of the white solid is removed from the tube and dissolved in water after a experiment. Describe how the white solid could be tested to show it contains ammonium ions? | Test: Add sodium hydroxide Results: Test gas with red litmus and the indicator will turns blue |
Some of the white solid is removed from the tube and dissolved in water after a experiment. Describe how the white solid could be tested to show it contains chloride ions? | Test: Add silver nitrate Results: Add nitric acid and white will precipitate. |
Nylon and proteins are both polymers containing nitrogen. Describe one difference in the structures of nylon and protein? | Proteins are made from more than two monomers and nylon is from only 2 monomers |
What is the general name given to the products of hydrolysis of proteins? | Acids |
Compound x is a hydrocarbon. It contains 85.7% of carbon. The mass of one mole of x is 84g. What is the percentage of hydrogen in the compound? | 14.3% |
Define the term diffusion? | Particles spread to fill total available volume from high concentration to low concentration and moves down a concentration gradient |
What property of a gas molecule affects the speed at which it didduses? | Mass of the gas molecule |
Helium is a gas used to fill balloons. It is present in very small quantities. Diffusion can be used to separate it from air. Air at 1000 degrees Celsius is on one side of a barrier. The air which passes through has more helium. Why? Name 3 points. | Helium molecules are lighter than molecules in the air Helium is less dense than air Helium diffuses faster than air |
Most helium is obtained from natural gas, Natural gas contains methane and 7% helium, One possible way to obtain the helium would be to burn the methane. Suggest why this would not be a suitable method to obtain helium? | You would get a mixture of helium and carbon dioxide. |
Suggest another method, other than diffusion, by which helium could be separated from the mixture of gases in natural gas? | Fractional distillation |
Explain the rate of most reactions increases at higher temperatures? Name 3 points. | Particles have more energy Particles move faster Particles collide more frequently |
A small amount of liquid bromine is added to a container which is then sealed. Use the ideas of the kinetic theory to explain why, after about an hour, the bromine molecules have spread uniformly to occupy the whole container. | The explanation of evaporation. Particles with a lot of energy leaves the liquid and bromine particles break free from each other |
Explain the term isotope? | Some numbers of protons |
Explain why two isotopes of the same element have identical chemical properties? | Same electron distribution |
How does the movement and arrangement of the molecules in a crystal of nitrogen differ from those in gaseous nitrogen? Name 3 points. | Solid pattern is regular and gas pattern is random Solid distance is close and gas distance is far apart Solid movement vibrate and gas movement moving around |
A sealed container contains nitrogen gas. The pressure of a gas is due to the molecules of the gas hitting the walls of the container. Explain why the pressure inside the container increases when the temperature in increased? | Particles molecules have more energy and move faster |
Explain why nitrogen diffuses faster than chlorine? | Nitrogen has smaller and lighter molecules and lower density nitrogen molecules and particles move faster than chlorine molecules. |
Explain why the nitrogen diffuses faster at the higher temperature? | At high temperature nitrogen molecules have more energy |
Three of the halogens in group VII are Chlorine, Bromine and iodine. How does their colour change down the group? | Chlorine: Yellow to green Bromine: Orange to brown Iodine: Black to Purple |
Three of the halogens in group VII are Chlorine, Bromine and iodine. How does their physical state (Solid, liquid or gas) change down the Group? | Solid, liquid and gas are needed |
Predict the colour and physical state of fluorine? | Colour: Yellos Physical state; Gas |
Describe how you could distinguish between aqueous potassium bromide and aqueous potassium iodide. | Test: Add Chlorine water in chlorine gas Bromide will be yellow Iodide will be dark brown |
Traces of chlorine can be separated from bromine vapour by diffusion. Which gas would diffuse the faster and why? | Chlorine Lower molecules |
Explain the difference in electrical conductivity between solid and liquid strontium chloride? | Ions cannot move in solid but can move in liquid |
Explain the difference in electrical conductivity between liquid strontium chloride and liquid sulphur chloride | No ions in Sulphur chloride Only strontium chloride has ions |
Ethylamine is a weak base and sodium hydroxide transfer is a strong base. In terms of proton transfer, explain what is meant by the term weak base. | Less able to accept Protons |
Gases diffuse, which means that they move to occupy the total available volume. Explain, using kinetic particle theory, why gases diffuse? Name 3 points. | Particles move in random motion Particles collide Particles move from a region of high concentration to low concentration |
The halogens are a collection of diatomic non=metals in Group VII. Define the term diatomic? | Two atoms per molecule |
What do the electron distributions of the halogens have in common? | Same number of outer electrons need to gain one electron |
How do their electron distributions differ? | Different number of energy levels and different number of electrons |
Photochromic glass is used in sunglasses. In bright light, the glass darkens reducing the amount of light reaching the eye. When the light is less bright the glass becomes colourless increasing the light. How does Photochromic glass work? | Light increases causes forward reaction Light increases the amount of silver and so darkens glass |
Selenium and sulfur are in Group VI. They have similar properties. The main use of selenium is in photoelectric cells. These cells can change light into electrical energy. Name a process which can change light into chemical energy? | Photosynthesis or a Photochemical reaction |
Name a device which can change chemical energy into electrical energy? | A Cell that accept a battery |