Matter, Mixtures and Separation

Which of these is a mixture?

What happens to the temperature of a pure liquid while it boils?

Which gas diffuses fastest at the same temperature? Relative molecular masses: chlorine 71, carbon dioxide 44, helium 4, oxygen 32.

Which separation method gives a pure solid from a solution of a substance that decomposes on heating?

A spot has an R_f of 0.40. The solvent front moved 10.0 cm. How far did the spot move?

Salt dissolves in water.

Substances can be classified as elements, compounds or mixtures. Which underlined substance best represents a mixture?

A student made four statements about elements, compounds and mixtures.

statement 1: Elements are made up of only one type of atom.
statement 2: Compounds have similar properties to the elements they are made of.
statement 3: Little or no energy change is involved when a compound is formed.
statement 4: Mixtures have a fixed ratio of components.

How many of the above statements are correct?

A new substance was discovered, and a series of experiments were conducted on it. Which observation suggests that the substance cannot be an element?

The conical flask contains compound X which is present in liquid and gaseous states. Which statement is correct?

The rate of diffusion of gas P (M_r = 32) and gas Q (M_r = 64) was compared at 30 °C and 60 °C. Which would have the slowest rate of diffusion?

What happens to the molecules when steam condenses to form water?

Dry ice sublimes at −78 °C. Which statement describes what happens to dry ice at 0 

A mixture is made up of two liquids whose boiling points differ by 52.5 °C. What other information about the liquids is necessary to identify the appropriate method to separate them?

Which statement is correct?

The table shows some mixtures and their constituents obtained using suitable separation techniques.

Which row gives the correct separation techniques to obtain the constituents from the mixture? Each option gives the technique for 1, 2 and 3 in that order.

The boiling points of four substances found in air are given in the table.

Air is cooled to −190 °C such that some substances condense into liquid. When the temperature is then raised, which liquid would turn into a gas first?

Which statement about chromatography is correct?

The table gives the results of chromatography experiments that were carried out on some known food colours, using the same solvent.

Which food colour is the most soluble in the solvent used?

A chemist is given an unknown white powder. What should the chemist do to determine the purity of the unknown substance?

A liquid is suspected to be pure ethanol. What is the best way to test its purity?

Which substance should be pure for the intended use?

An impure sample of compound X has a melting point of around 120 °C. X is purified and its melting point is measured again. Which row is correct? Each option gives the method of purification, then the melting point of pure X.